Intrinsic Flame‐Retardant Solid–Solid Organic Phase Change Materials for High‐Security Thermal Management

Abstract Organic phase change materials (PCMs) provide great potential for zero‐energy thermal management thanks to superior thermal storage cyclability, stable phase change temperature, and low supercooling behavior. However, liquid leakage and flammability are long‐standing defects that limit their practical utilization in thermal management. Here, an intrinsic flame‐retardant solid–solid organic phase change material synthesis strategy is realized by a facile multicomponent reaction (MCR) from dimethyl phosphite, benzaldehyde, and alcohol under mild conditions. Owing to the presence of phosphine oxygen bond, the dipole moment of the PCMs is enhanced, thereby an elevated intermolecular interaction is attained, which works along with π–π stacking force and hydrogen bonding to restrain the amorphous state to a solid appearance above the melting temperature. In the meantime, the phosphine oxygen bond endows robust flame‐retardancy to PCMs by forming phosphates in the condensed phase. A deep insight behind the crystal‐to‐amorphous transition process is revealed through experimental and density functional theory (DFT) calculations by varying the chain length of alcohol. Notably, the easily accessible raw materials and facile operation technique render the strategy applicable across diverse organic PCMs. High‐security thermal management in wooden furniture and lithium‐ion batteries (LIBs) is further demonstrated, and it is revealed the safe working time of LIBs can be prolonged almost 100 times compared with blank setups.